A novel difficulty scoring system for laparoscopic liver resection.

Early on, laparoscopic liver resection (LLR) was limited to partial resection, but major LLR is no longer rare. A difficulty scoring system is required to guide sur- geons in advancing from simple to highly technical laparo- scopic resections. Subjects were 90 patients who had undergone pure LLR at three medical institutions (30 patients/institution) from January 2011 to April 2014. Sur- gical difficulty was assessed by the operator using an index of 1-10 with the following divisions: 1-3 low difficulty, 4-6 intermediate difficulty, and 7-10 high difficulty. Weighted kappa statistic was used to calculate the concordance between the operators' and reviewers' (expert surgeon) dif- ficulty index. Inter-rater agreement (weighted kappa statis- tic) between the operators' and reviewers' assessments was 0.89 with the three-level difficulty index and 0.80 with the 10-level difficulty index. A 10-level difficulty index by linear modeling based on clinical information revealed a weighted kappa statistic of 0.72 and that scored by the extent of liver resection, tumor location, tumor size, liver function, and tumor proximity to major vessels revealed a weighted kappa statistic of 0.68.We proposed a new scoring system to predict difficulty of various LLRs preoperatively. The calculated score well reflected difficulty.